Improved fluid flow sensor configuration

Abstract

An improved fluid flow sensor configuration comprises a thin membrane of a low thermally conductive material having one surface in thermal contact with the heating and temperature sensitive elements of a fluid flow sensor and the other surface in thermal contact with a fluid whose flow rate is measured by the fluid flow sensor.

What is claimed is: 
     
       1. A fluid flow sensor configuration comprising: a conduit adapted to contain a fluid, said conduit including a live-flow channel and a dead-flow channel,   a first electrical element and a second electrical element positioned to be adjacent to and in thermal contact with said fluid respectively in said dead-flow channel and said live-flow channel of said conduit, said first and said second electrical elements, in combination with additional circuitry, adapted to sense the flow of said fluid in said live-flow channel,   a thin membrane of thermally conductive material positioned to be between said fluid and said electrical elements and having a first surface thereof adjacent to and in thermal contact with both of said electrical elements, said membrane having a thickness of approximately 250 micrometers or less and a thermal conductivity of approximately 0.08 cal/cm--sec°C or less in order to minimize the lateral transfer of heat throughout said membrane while keeping said electrical elements thermally coupled to said fluid, and   means for supporting a second surface of said membrane adjacent to and as a portion of the boundary of said conduit whereby said membrane is disposed between said fluid and said electrical elements.   
     
     
       2. The fluid flow sensor configuration as defined in claim 1 wherein said first and said second electrical elements are semiconductor chips. 
     
     
       3. The fluid flow sensor configuration as defined in claim 2 wherein said first semiconductor chip comprises an integrated circuit chip having the two ends thereof positioned to be in thermal contact with said fluid in said live-flow and said dead-flow channels respectively. 
     
     
       4. The fluid flow sensor configuration as defined in claim 2 wherein said means comprises a means for mounting said membrane adjacent to an opening in each of said live-flow and said dead-flow channels, separate portions of said second surface of said membrane completely covering each of said openings respectively whereby said separate portions of said second surface contact said fluid in said conduit. 
     
     
       5. The fluid flow sensor configuration as defined in claim 4 further comprising a substrate of insulating material to which said first and said second semiconductor chips are affixed, said substrate having a first surface thereof disposed adjacent to said first surface of said membrane and having circuitry connected to said first and said second chips and disposed on a second surface thereof whereby said membrane is insulated from said circuitry. 
     
     
       6. The fluid flow sensor configuration as defined in claim 5 wherein said mounting means comprises: a sealing gasket disposed between said membrane and said conduit and having two holes therein, said holes exposing said portions of said second surface of said membrane to said fluid, and   a cover positioned adjacent to a layer of insulating material and attached by fastening means to said conduit, said layer of insulating material being disposed between said second surface of said substrate and said cover whereby said first and said second semiconductor chips are electrically insulated from said cover.   
     
     
       7. The fluid flow sensor configuration as defined in claim 5 wherein said substrate is a printed circuit board.